Non-thyroid cancer incidence in Belarusian residents exposed to Chernobyl fallout in childhood and adolescence: Standardized Incidence Ratio analysis, 1997-2011.

BACKGROUND: While an increased risk of thyroid cancer from post-Chernobyl exposure to Iodine-131 (I-131) in children and adolescents has been well-documented, risks of other cancers or leukemia as a result of residence in radioactively contaminated areas remain uncertain. METHODS: We studied non-thyroid cancer incidence in a cohort of about 12,000 individuals from Belarus exposed under age of 18 years to Chernobyl fallout (median age at the time of Chernobyl accident of 7.9 years). During 15 years of follow-up from1997 through 2011, 54 incident cancers excluding thyroid were identified in the study cohort with 142,968 person-years at risk. We performed Standardized Incidence Ratio (SIR) analysis of all solid cancers excluding thyroid (n=42), of leukemia (n=6) and of lymphoma (n=6). RESULTS: We found no significant increase in the incidence of non-thyroid solid cancer (SIR=0.83, 95% Confidence Interval [CI]: 0.61; 1.11), lymphoma (SIR=0.66, 95% CI: 0.26; 1.33) or leukemia (SIR=1.78, 95% CI: 0.71; 3.61) in the study cohort as compared with the sex-, age- and calendar-time-specific national rates. These findings may in part reflect the relatively young age of study subjects (median attained age of 33.4 years), and long latency for some radiation-related solid cancers. CONCLUSIONS: We found no evidence of statistically significant increases in solid cancer, lymphoma and leukemia incidence 25 years after childhood exposure in the study cohort; however, it is important to continue follow-up non-thyroid cancers in individuals exposed to low-level radiation at radiosensitive ages.

Second Primary Cancer Among Patients With Papillary Thyroid Carcinoma Following the Chernobyl Disaster.

Importance: To our knowledge, there are no complete population-based studies of the risks of developing second malignant tumors after papillary thyroid carcinoma (PTC) in patients following the Chernobyl nuclear accident. Objective: To study the risk of second primary cancers in patients with PTC after the Chernobyl disaster. Design, Setting, and Participants: This was a retrospective cohort study conducted in the Republic of Belarus over a 31-year time frame evaluating patients with primary PTC and second malignant tumors. Personal data from the Belarussian Cancer Registry were used in the investigation, and only second primary cancers were included in the analysis. Patients were observed from January 1, 1990, to December 31, 2021, for the establishment of second primary malignant tumors. Main Outcomes and Measures: For analysis, synchronous and metachronous tumors were grouped into 1 group (second primary cancer group). If the patient had more than 2 cancers, they were observed until development of a second tumor and, subsequently, the development of a third tumor. The starting point for calculating the number of person-years was the date of thyroid cancer diagnosis. The end point for calculating the number of person-years was the date of diagnosis of the second primary malignant tumor, the date of death, the date of the last visit of the patient, or December 31, 2021 (the end the of study period). The incidence of a second primary malignant tumor with PTC was calculated for the study groups using standardized incidence ratios. Results: Of the 30 568 patients with a primary PTC included in this study, 2820 (9.2%) developed a second malignant tumor (2204 women and 616 men); the mean (SD) age of all patients at time of the primary cancer was 53.9 (12.6) years and at time of the secondary cancer was 61.5 (11.8) years. Overall, the standardized incidence ratio was statistically significant for all types of cancer (1.25; 95% CI, 1.21-1.30), including solid malignant tumors (1.20; 95% CI, 1.15-1.25) and all leukemias (1.61; 95% CI, 2.17-2.13). Cancers of the digestive system (466 cases [21.1%]), genital organs (376 cases [17.1%]), and breasts (603 cases [27.4%]) were the most prevalent second primary tumors in women following PTC. Second primary tumors of the gastrointestinal tract (146 cases [27.7%]), genitourinary system (139 cases [22.6%]), and urinary tract (139 cases [22.6%]) were the most prevalent in men. Urinary tract cancers (307 cases [10.9%]) and gastrointestinal tumors (612 cases [21.4%]) were the most prevalent second primary tumors overall. Conclusions and Relevance: This cohort study reports the increased incidence of solid secondary tumors in men and women over a 31-year time frame after the Chernobyl disaster. Moreover, there was a statistically significant increased risk of second tumors of the breast, colon, rectum, mesothelium, eye, adnexa, meninges, and adrenal glands as well as Kaposi sarcoma. These data might have an effect on the follow-up of this cohort of patients to detect secondary malignant tumors at an early stage.

Second primary malignancies in patients with papillary thyroid carcinoma after effect of post-chernobyl irradiation: A risk analysis of more than two decades of observations.

BACKGROUND: Second primary malignancy in patients with papillary thyroid carcinoma after Chernobyl accident is an emerging problem. The aims of the study are to investigate the rates and distribution of second primary malignant tumours in Belarus survivors of post-Chernobyl papillary thyroid carcinoma and the cumulative rate of developing a second primary malignancy in a group of patients with metachronous second primaries. METHODS: Patients aged 18 or younger at the time of Chernobyl accident who were diagnosed with papillary thyroid carcinoma after 1986 were identified from the Belarus Cancer Registry. The clinical and demographic of these patients were analysed to correlate with the factors for the development of secondary primary cancer. RESULTS: Secondary primary cancer was detected in 1.8 % (119 of 6559) of the patients with papillary thyroid carcinoma. The cumulative incidence tended to rise with increasing age of the cohort and varied depending on the sex of patients. In female patients, breast carcinoma and genital tract carcinomas prevailed, in men patients - lymphoma/ leukaemia and the alimentary tract malignancies predominated. A significant excess risk was revealed for breast carcinoma in females, colon carcinoma in males, and the urinary system carcinomas in males (absolute excess risk [AER] = 3.23, 3.01 and 2.17 correspondingly). Overall, our results pointed to the increased risk of new solid primaries in females, males and both genders (AER = 3.31, 7.19, 4.28 correspondingly) as well as increase risk of lymphoid/hematopoietic malignancies in females and both genders (AER = 1.24) and leukaemia in male patients (AER = 1.45). CONCLUSION: Patients with papillary thyroid carcinoma after Chernobyl accident are at risk of secondary primary malignancy. Awareness and screening of secondary cancer is needed for patients with papillary thyroid carcinoma after Chernobyl accident.

Comparative pathological characteristics of papillary thyroid carcinoma with second primary non-thyroid malignancies in the region affected by the Chernobyl accident.

The aim was to study the pathological features of papillary thyroid carcinoma diagnosed with or before second primary malignancy in patients exposed to post-Chernobyl exposure. The patients selected (n = 6559) were those exposed to radiation at the age of ≤ 18 years old and developed papillary thyroid carcinoma during the years 1990-2020. Of these, 2.1% (n = 140) had second primary malignancies. To compare the histopathological characteristics of papillary thyroid carcinoma in the group under analysis, 91% (n = 128) with sufficient data were included in further analysis. The control group was formed by matching patients with age at exposure to radiation, age at surgery, gender, and place of residence. Median age at exposure was 14 years old for both groups. Besides, no difference in tumour extension and histological features of papillary thyroid carcinoma was noted between patients with synchronous or metachronous primary malignant tumours. Nevertheless, the time lag to the diagnosis of papillary thyroid carcinoma was shortened in the group with metachronous when compared to patients with synchronous second primaries (p < 0.001). Independent differences between patients with second primaries and their matched peers included tumour size {OR (95%CI) = 0.89 (0.45; 1.04)}, multiple tumours {OR (95% CI) = 1.46 (0.86; 2.42)}, lymphatic vessel invasion (OR (95%CI) 0.92 (0.61; 1.53)), blood vessel invasion (OR (95%CI) 0.41 (0.10; 1.23) and presence of numerous psammomas (OR (95%CI) 0.73 (0.39; 1.31)). The possible influence of radiative iodine treatment for development of second primaries was analysed for the group of patients with metachronous malignancies using the same approach (84 patients were compared to 252 matched patients). Independent differences also included tumour size {OR (95% CI) 0.77 (0.45; 1.30)}, lymphatic vessel invasion {OR (95%CI) 0.75(0.43; 1.28)}, blood vessel invasion {OR (95%CI) 0.17 (0.01; 0.87)}. Besides, multiple tumours were revealed more frequently in patients with metachronous primaries (OR (95%CI) 1.92 (1.0; 3.62)). To conclude, patients exposed to Chernobyl irradiation with the development of papillary thyroid carcinoma and second primary malignancy have less biological aggressive pathological characteristics of their thyroid cancers. Accordingly, these patients were less frequently treated with post-surgical radioactive iodine. Thus, 131I-irradiation may have negligible impact on the development of second primaries.